The density of mitochondria can vary tremendously, depending on cell size and type. This image shows a dense cluster of mitochondria in the Golgi region of a Leydig cell of the domestic boar, Sus scrofa. Figure 253 from Chapter 7 (Mitochondria) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.